Injection device

ABSTRACT

An injection device is described which is lockable in its end position in such a manner that the reliability of storing or transporting it with a carpule attached is improved in comparison with devices according to the prior art. It is comprised of fewer components than comparable devices, with these components being easier to manufacture so that production costs are low. The injection device is used for medical purposes.

RELATED APPLICATIONS

This application claims the priority of PCT application No.PCT/CH95/00262, filed Nov. 9, 1995, which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device for repeatedly injectingdosages of a liquid medicament from a container for liquids, especiallya carpule (=injection ampoule), equipped with a piston, said containerbeing attachable to or detachable from a manually drivable transmissionincorporated into a transmission sleeve, said transmission comprising adrive member comprised of a guide button and a carrier sleeve firmlyattached thereto, said drive member being disposed rotatably andshiftably in the advance direction of the piston in the transmissionsleeve, a driven member comprised of a threaded rod and a flange, saiddriven member being shiftable in the advance direction of the piston andbeing carriable over a certain distance under the influence of the drivemember executing longitudinal shifts, a transmission element beingscrewably disposed on the threaded rod and having the effect of thedriven member being carried along by the drive member, a compressionspring acting between the transmission sleeve and the carrier sleeve, inwhich the drive member is lockable by a locking device, the threaded rodof the driven member is disposed nonrotatably and shiftable in thelongitudinal direction in the transmission sleeve, and the transmissionelement is rotatable but attached shiftably in the longitudinaldirection to the drive member.

2. Description of the Prior Art

Such injection devices have been known for some time, for example adevice described in EP-0 245 312 B1 which must be regarded as theclosest prior art. It has the purpose of injecting respectivelyselectable amounts of liquid from a container for liquids equipped witha piston, especially a carpule (=injection ampoule).

Said carpule in a carpule holder is attachable to or detachable from amanually drivable transmission. The transmission is incorporated into atransmission sleeve. In addition to other parts, it comprises

a drive member comprised of a guide button and a carrier sleeve firmlyattached thereto, said drive member being disposed rotatably andshiftably in the advance direction of the piston in the transmissionsleeve,

a driven member comprised of a threaded rod and a flange, said drivenmember being shiftable in the advance direction of the piston and beingcarriable over a certain distance under the influence of the drivemember executing longitudinal shifts,

a transmission element being screwably disposed on the threaded rod,

a compression spring acting between the transmission sleeve and thecarrier sleeve.

While being operated, the injection device may be in the followingpositions:

a home position, where the drive member is at its furthest possibledistance from the piston and the transmission element is close to thepiston,

an intermediate position where the drive member remains in its position,but the transmission element, depending on the amount of liquid to beinjected, is further away from the piston than in its home position,

a final position where the drive member is closer to the piston and thedriven member has protruded further from the transmission than in thehome or intermediate position and has penetrated into the carpule whichcauses injection of the selected amount of liquid.

The final position reverts to the home position by itself.

The transmission is not locked in any of the three positions so that itmay be exposed to influences during storage or transport of theinjection device which may cause a change in the amount of liquid in thecarpule or even permit the entry of air into the carpule. In addition,it has many components, some of which are not very easy to manufacture.

SUMMARY OF THE INVENTION

The invention is based on the objective to provide an injection devicewhich is self-lockable in at least one position which is then regardedas the final position.

The subject matter of claim 1 is the solution of this objectiveaccording to the invention. Preferred additional embodiments of theinvention are described in detail in the ensuing claims. The injectiondevice described in these claims can be comprised of fewer componentsthan comparable devices with the components being easier to manufacturethan known injection devices.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, one embodiment of the invention will be illustrated indetail on the basis of the drawing, wherein

FIG. 1 shows an axial longitudinal section through the injection deviceaccording to the invention in one final position;

FIG. 2 shows the same in a home position; and

FIG. 3 shows the same in an intermediate position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The injection device shown in FIGS. 1 to 3 has a carpule part 1 and atransmission 2 which is easily attachable and detachable, for example bymeans of a thread or a bayonet socket.

The carpule part 2 comprises a container 3 for liquids, hereinaftercalled "carpule" 3, filled with the liquid to be injected, a carpuleholder 4, a piston 5 which is in contact with the liquid at all timesand displaces the liquid to be injected during the act of injecting, aneedle holder 6 and a needle 7 from which the liquid to be injected isejected.

The transmission 2 is incorporated in a transmission sleeve 8. Itcomprises

a drive member 12, comprised of a guide button 32 and a carrier sleeve13 firmly attached thereto, said drive member being disposed rotatablyand shiftably in the advance direction of the piston 5 in thetransmission sleeve 8,

a driven member 9, comprised of a threaded rod 39 and a flange 10, saiddriven member being shiftable in the advance direction of the piston 5and being carriable over a certain distance under the influence of thedrive member 12, 13 executing longitudinal shifts,

a transmission element 11 being screwably disposed on the threaded rod 9and having the effect of the driven member 9, 10 being carried along bythe drive member 12, 13,

a compression spring 14 held by a spring sleeve 15 and acting betweenthe transmission sleeve 8 and the carrier sleeve 13.

The injection device according to the invention has the followingconstructive features:

A locking device 16, 17, 20, 21 engages with the drive member 12, 13.

The threaded rod 9 of the driven member 9, 10 is disposed non-rotatablybut shiftably in the longitudinal direction in the transmission sleeve8.

The transmission element 11 is non-rotatable but attached shiftably inthe longitudinal direction to the drive member 12, 13.

The flange 10 of the drive member 9, 10 is contiguous to the piston 5being in contact with the liquid as long as the carpule 3 is connectedto the transmission 2.

It has the properties described below:

At the end of each injection, the transmission 2 is in a locked endposition (FIG. 1) in which end position (FIG. 1) it may also be storedand transported. In this end position (FIG. 1), the drive member 12, 13protrudes relative to the transmission sleeve 8 so far in the advancedirection towards the piston 5 that the lock 16, 17, 20, 21 between thetransmission sleeve 8 and the drive member 12, 13 engages and secures itagainst rotation and shifting in the longitudinal direction. Inaddition, the transmission element 11 is in contact with a first stopper18 on the transmission sleeve 8 in the direction of the piston 5 whichlimits said transmission sleeve in the direction of the piston.

When the lock 16, 17, 20, 21 is engaged, the drive member 12, 13 isneither rotatable nor shiftable. Therefore, it is not possible tooperate the injection device--not even intentionally--while it is in thefinal position (FIG. 1) and thus it cannot lose any liquid. Thisdistinguishes it from the injection devices known previously.

The lock 16, 17, 20, 21, for example, consists of a locking ring 16encircling the drive member 12, 13 and a cam 20 connected therewith.Said cam is positioned in the transmission sleeve 8 and when pressed bya spring 17 engages in the drive member 12, 13 in the final position.Said cam can only be released from the groove 21 by pressing the lockingring 16 against the spring 17. Once the lock 16, 17, 20, 21 has beenreleased, the drive member 12, 13 is once again rotatable and shiftableand is pushed by the compression spring 14 into the home position (FIG.2) described below. However, a lock having comparable properties mayalso be designed in a different manner.

In order to carry out another injection, the transmission 2 is firstbrought into a home position (FIG. 2). In said home position, the drivemember 12, 13 is pushed as far as possible away from the piston 5opposed to the advance direction of the piston and this is effected bythe compression spring 14 which pushes the drive member 12, 13 by adistance H up to a second stopper 19 on the transmission sleeve 8. Saidsecond stopper 19 is, for example, an annular ring on the surface of theinner jacket of the transmission sleeve 8. The transmission element 11is still contiguous to the first stopper 18 of the transmission sleeve(8) in the direction of the piston 5. The shift from the final position(FIG. 1) to the home position (FIG. 2) is effected by releasing the lock(16, 17, 20, 21) of the transmission sleeve 8 and the drive member 12,13, said drive member 12, 13 becoming rotatable and shiftable in thelongitudinal direction and the compression spring 14 shifting the drivemember 12, 13 opposed to the advance direction of the piston (5) intothe home position (FIG. 2).

From the home position (FIG. 2), the transmission 2 is brought into anintermediate position (FIG. 3) which is determined by the amount ofliquid to be injected with the next injection. In said intermediateposition, the lower end of the transmission element 11 is shifted by adistance X relative to the first stopper 18 on the transmission sleeve 8opposed to the advance direction of the piston 5, said distance X beingdetermined by with I being the amount of liquid to be injected and Fbeing the inner cross sectional area of the carpule.

The shift from the home position (FIG. 2) to the intermediate position(FIG. 3) is effected by rotating the drive member 12, 13 in such adirection that the transmission element 11 which is connected shiftablyin the longitudinal direction and rotatable with the drive member 12, 13is rotated around its axis, the threaded rod 9, in such a manner that itis shifted along said threaded rod 9 opposed to the advance direction ofthe piston 5 by the distance X.

The transmission element 11 is shiftable to a third stopper 22 on thecarrier sleeve 13 at most. Said stopper is positioned against theadvance direction of the piston on the inner jacket surface of the drivemember at a distance A+H from the first stopper 18, with

A being the length of the transmission element (11)

H being the travel distance of the drive member between the finalposition (FIG. 1) and the home position (FIG. 2).

The following applies for the maximum shift distance H:

    H≧X.

From the intermediate position (FIG. 3), the transmission is broughtinto the final position (FIG. 1). During this time the injectionprocedure is carried out. For this purpose, the drive member 12, 13 isshifted by the distance H in the advance direction of the piston. Duringthis advance shift, the drive member 12, 13 carries the transmissionelement 11 forward which is positioned at a distance X from the firststopper 18 on the transmission sleeve 8. From that point onwards, thetransmission element 11 carries the driven member 9, 10 which isshiftable only the longitudinal direction along by the distance X.During this operation, the flange 10 thereof pushes the piston 5 in thecarpule 3 forward so that the amount of liquid I=F×X is displaced on thewhole and ejected through the needle 7 (injection). When the drivemember 12, 13 has travelled the distance H and the transmission element11 has travelled the distances X at the same time, the lock 16, 17, 20,21 engages into the drive member 12, 13. Thus the transmission 2 comesto rest in the final position, the drive member 12, 13 is no longerrotatable or shiftable in the longitudinal direction and the injectiondevice thus protected against a loss of liquid.

After the entire liquid in the carpule 3 has been consumed, the carpulepart 1 is detached from the transmission 2 in the home position (FIG.2). Then the driven member 9, 10 must be pushed back by rotating thedrive member 12, 13 in the reverse direction of the shift from the homeposition (FIG. 2) into the intermediate position (FIG. 3) until theflange 10 comes to rest on the stopper 23 of the transmission sleeve 8.

Advantageously the new carpules 3 to be inserted are filled in such amanner that the piston 5 is pushed forward a little by the flange 10during incorporation into the injection device and some liquid isejected from the needle 7. This ensures that no air is injected evenduring the first injection with the new carpule 3.

The injection devices according to the invention may be equipped withelectrical, optical or acoustic means capable of indicating the selecteddistance X. This may, for example, be a ratchet which acts between thedriven member (9, 10) and the transmission sleeve (8).

The injection device according to the invention has a lock 16, 17, 20,21 which prevents even intentional operation while it is in the finalposition (FIG. 1). This means that it may be stored and transported morereliably even with the carpule 3 attached than devices according to theprior art. Moreover, it is comprised of fewer components some of whichare easier to manufacture so that the required production costs arelower.

I claim:
 1. A transmission for an injection device for injecting anamount of liquid from a container equipped with a piston, the containerbeing attachable to and detachable from the transmission, thetransmission having home, end and intermediate positions andcomprising:a transmission sleeve having a generally central longitudinalaxis; a drive member comprising a guide button and a carrier sleevefixedly attached to the guide button, said drive member being disposedrotatably and axially shiftably in the transmission sleeve, a drivenmember comprising a threaded rod and a flange, said threaded roddisposed nonrotatably and axially shiftably in the transmission sleeve,said driven member being shiftable axially in the transmission sleeveover a distance under the influence of the drive member executing axialshifts, a transmission element being screwably disposed on the threadedrod whereby the driven member is moved axially by the drive member, saidtransmission element shiftible axially with respect to the drive member,and a lock for locking the transmission in the end position, said lockoperatively coupling the transmission sleeve and the drive member,whereby said lock engages and secures said drive member against rotationand axial shifting.
 2. The transmission according to claim 1, in which ashift from the end position into the home position is effected byloosening the lock between the transmission sleeve and the drive member,whereby the drive member is then rotatable and axially shiftable intothe home position.
 3. The transmission according to claim 2, in whichthe lock comprises a locking ring and a cam positioned in thetransmission sleeve and pressed against the drive member by a spring,said cam engaging in a groove on the drive member in the end positionand being releasable from said groove by pressing the locking ring. 4.The transmission according to claim 1, wherein the piston has aninjection delivering advance direction of movement, and wherein thetransmission's move from the intermediate position to the end positionis effected by axially shifting the drive member in the advancedirection of piston movement, wherein the drive member carries thetransmission element in an axial movement over a distance from a firststopper on the transmission sleeve in the advance direction of thepiston, and further wherein starting from said distance, thetransmission element carries the driven member in an axial shift untilthe transmission element pushes against the first stopper on thetransmission sleeve, whereby a flange associated with the driven memberpushes the piston into the container over said distance whereby aselected amount of liquid to be injected is discharged from thecontainer.
 5. The transmission according to claim 4, wherein the lockengages the drive member when the transmission element reaches thestopper on the transmission sleeve, whereby the drive member is lockedin the end position and may not be rotated or shifted in an axialdirection.
 6. The transmission according to claim 4, wherein theintermediate position is selectable and wherein when in saidintermediate position, an end of the transmission element is positioneda distance X from the first stopper in a direction generally opposite tothe advance direction of the piston.
 7. The transmission according toclaim 6, wherein the distance X is determined by the amount of liquid tobe injected divided by the inner cross-sectional area of the container.8. An injection device for injecting a selectable amount of liquid, saidinjection device comprising:a carpule having a piston with an injectingdirection of movement; a manually drivable transmission, said carpulebeing attachable to and detachable from said transmission, saidtransmission comprising:a transmission sleeve, said transmission sleevegenerally tubular and having a generally central longitudinal axis; adrive member comprising a guide button and a carrier sleeve firmlyattached to said guide button, said drive member being disposedrotatably and axially shiftably in the transmission sleeve; a drivenflange member comprising a threaded rod and a flange, said driven memberbeing axially shiftable in the transmission sleeve and being carriableover a certain distance under the influence of the drive memberexecuting axial shifts; a transmission element screwably disposed on thethreaded rod, whereby the driven member is carried by the drive member;a compression spring acting between the transmission sleeve and thecarrier sleeve; and a lock operably coupling the transmission sleeve andthe drive member for locking the drive member, whereby said lock engagesand secures said drive member against rotation and axial shifting. 9.The injection device according to claim 8, wherein the threaded rod isdisposed nonrotatably and axial shiftably in the transmission sleeve,and the transmission element is rotatable and attached axially shiftablyto the drive member.
 10. The injection device according to claim 8,wherein at the end of an injection, the transmission is in a locked endposition in which the drive member is positioned near the piston, andwherein in order to prepare another injection the transmission is firstmoved into a home position wherein the drive member is at a distancefrom the piston and from said home position is moved into an adjustableintermediate position from which said transmission is moved to thelocked end position thereby performing an injection.
 11. The injectiondevice according to claim 10, wherein the move from the home positioninto the intermediate position is accomplished by turning the drivemember in such a direction that the transmission element is moved alongthe threaded rod.
 12. The injection device according to claim 10,wherein in the home position the drive member is urged by thecompression spring in a direction opposite to the injecting direction ofmovement of the piston whereby the drive member stops at one stopperassociated with the transmission sleeve, and wherein the transmissionelement remains stopped at another stopper of the transmission sleeve.13. The injection device according to claim 12, further comprising anindicating means for indicating the selected amount of liquid to beinjected, said indicating means consisting of one of the group ofelectrical, optical or acoustical indicating means for indicating theselected amount of liquid to be injected.
 14. The injection deviceaccording to claim 13, wherein the indicating means comprises anacoustical means comprising a ratchet operably coupled between the drivemember and the transmission sleeve.
 15. The injection device accordingto claim 10, wherein the selected adjustment of the intermediateposition determines the amount of liquid to be injected.
 16. Theinjection device according to claim 10, wherein the lock automaticallyand positively locks the transmission in the locked end position.